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Piston ring wear measurements were carried out in a standard production 2.3-liter engine using compression rings that had been subjected to bulk thermal neutron bombardment. As the radioisotopes produced by this process were worn from the rings during each test run, they served as irradiated tracers for the detection of wear particles. A total of 32 tests were conducted on six different oils. All oils showed two distinct types of wear. The first, start-up wear, is characterized by a high wear rate and a relatively short duration. The second, steady-state wear, showed a much lower wear rate and continued in a constant manner for the remainder of the test. The start-up ring wear rate was substantially larger than the steady-state wear rate. The addition of a unique boundary chemistry engine treatment substantially reduced both the total amount of piston ring wear, and the rate at which wear particles were produced during start-up.

A mechanism was proposed in SAE Paper #941983, (October, 1994) to explain why “Unique Boundary Chemistry” (UBC) described in said paper (1) required an extended conditioning period for its full antiwear benefits to be realized and (2) why the UBC Chemistry produced a strong antiwear carryover effect, even after relatively short exposure to the engine. This paper will document and discuss results from several metal surface studies employing a variety of metal surface analysis techniques (XPS, Profilometry, and AFM) to support various aspects of the earlier proposed antiwear mechanism. These surface analysis studies were carried out with pertinent boundary lubricated parts from (a) bench tests, (b) engines tested under modified protocol Sequence IIIE conditions described in SAE Paper 941983 and (c) standard ASTM Sequence IIIE and VE tests exposed to the UBC Chemistry.

A unique combination of boundary lubricant and surfactant chemistries has produced significant benefits in ring and bearing wear control. This chemistry is added as an engine treatment to current quality engine lubricants. Microscopic wear studies employing radioactive tracer and metal surface analysis techniques have helped define optimum chemistry for enhanced bearing and ring wear control in a running engine. These studies have also served to further our understanding of the wear protection mechanism. Results from macroscopic engine wear studies, carried out in Sequence IIIE engines/stands using modified ASTM IIIE protocols, paralleled data obtained from the radioactive wear studies. They confirmed the positive wear protection benefits of this unique chemistry. Vehicle emission evaluations using the Federal Test Procedure (FTP) for light duty vehicles with this unique chemistry showed no detrimental effects either as added pollutants or catalyst degradation.